High-Temperature Mechanical Properties of Al6.9Ti6.9Cr15.5Fe34.5Ni36.2 Clad High-Entropy Alloy—Analysis of Nanoscale Strengthening Mechanisms

This study integrated the design concepts of high-entropy alloys and traditional superalloys to develop a precipitation-strengthened overlay high-entropy alloy, Al[Formula: see text]Ti[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]Ni[Formula: see text]. The study focused on revealing the nucleation, growth and interaction mechanisms of L12 precipitated with dislocations at the nanoscale, combined with the synergistic effects of BCC/B2 phases. This article systematically analyzed the high-temperature mechanical properties, microstructure evolution, and dislocation motion laws of alloys from room temperature to [Formula: see text]C. The results indicated that the dispersed nanoscale L12 (Ni3 (Al, Ti)) phase (particle size [Formula: see text] 50[Formula: see text]nm) in the post-weld alloy matrix serves as the core strengthening phase, forming a semi-coherent interface with the FCC matrix. Strengthening and toughening were achieved through mechanisms such as dislocation cutting and interface pinning. The microstructure of the alloy was basically stable from room temperature to [Formula: see text]C, and a small amount of [Formula: see text] brittle phase precipitated at [Formula: see text]C. Significant coarsening of dendrites and BCC phase at [Formula: see text]C; The tensile strength of the alloy decreased with increasing temperature, with tensile strengths of 806.1[Formula: see text]MPa and 127.4[Formula: see text]MPa at room temperature and [Formula: see text]C, respectively. The strength at all temperatures was higher than that of the traditional Inconel 625 high-temperature alloy. The dislocation motion was mainly planar slip from room temperature to [Formula: see text]C, and the L12 nanophase was strengthened by the synergistic effect of slip plane softening and dislocation dipole array. Above [Formula: see text]C, dislocations underwent polygonization dominated by climb and cross slip, while the L12 phase still delayed matrix softening through interface strengthening. The secondary nano precipitation of BCC/B2 phase further regulated dislocation pile-up and stress concentration, achieving synergistic strength and plasticity at high temperatures.